Sanitary control valves are generally used in biotechnology and pharmaceutical applications that require clean or sterile processing. Typical sanitary control valves include an actuator portion and a control portion. The actuator portion includes an actuator diaphragm that is coupled to a longitudinally-disposed actuator stem, and compressed fluid introduced into an actuation chamber acts on the diaphragm to displace the actuation stem along its axis.
When the actuator stem is downwardly displaced, the distal end of the actuator stem engages a linkage body having a pair of engagement arms pivotably secured thereto, thereby causing the engagement arms to outwardly displace as the actuator stem causes the engagement arms to pivot. A roller disposed at the distal end of each engagement arm provides a downward force against a compression plate such that the compression plate downwardly displaces. Because the engagement arms are pivotably coupled to the linkage body, the arms act as a lever multiplying the downward force applied to the top surface of the compression plate. The compression plate has a bottom surface that engages a control diaphragm, and the downward displacement of the compression plate causes a portion of the control diaphragm to engage a valve seat to prevent flow from a valve inlet to a valve outlet. When the actuator stem is subsequently upwardly displaced, a spring biases the compression plate upwards such that the control diaphragm is longitudinally spaced from the valve seat, thereby allowing flow from the valve inlet to the valve outlet.
In such a configuration, debris or shavings that have accumulated on the top portion of the compression plate can damage the compression plate and/or the rollers over time as the rollers engage the compression plate. Such damage could severely reduce the force multiplication provided to the compression plate and result in a corresponding reduction in diaphragm sealing performance. In addition, the linkage body assembly has a large number of moving parts, and maintenance and replacement of damaged and worn parts increases costs and the amount of time the valve is taken out of service.